The present invention is generally directed to mass analyzers. More particularly, the present invention is directed to a mass analyzer having an improved mass filter and/or ion detection arrangement that facilitates parallel processing of one or more analytes.
The characteristics of mass spectrometry have raised it to an outstanding position among the various analysis methods. It has excellent sensitivity and detection limits and may be used in a wide variety of applications, e.g. atomic physics, reaction physics, reaction kinetics, geochronology, biomedicine, ion-molecule reactions, and determination of thermodynamic parameters (xcex94Gxc2x0f, Ka, etc.). Mass spectrometry technology has thus begun to progress very rapidly as its uses have become more widely recognized. This has led to the development of entirely new instruments and applications.
Development trends have gone in the direction of increasingly complex mass analyzer designs requiring highly specialized components and tight manufacturing tolerances. Longer analysis times are often associated with this increased complexity. This, in turn, requires system designers to make significant design trade-offs between the accuracy of the mass measurements and the time required to obtain those measurements. However, such trade-offs have become increasingly intolerable in the competitive field of drug discovery and analysis. There, mass analyzers must be both highly accurate and provide for a high throughput of analytes.
One attempt to improve on existing mass analyzers is shown in U.S. Pat. No. 5,726,448, issued Mar. 10, 1998, to Smith et al. The ""448 patent purportedly describes a mass analyzer having a mass filter chamber that employs a rotating RF electric field for ion sample separation. Rotation of the electric field is achieved through the use of at least four electrodes that operate in opposed parallel pairs. A first RF signal is applied to the first pair of parallel electrodes while a second RF signal is applied to the second pair of parallel electrodes. The first and second RF signals differ in phase by xcfx80/2 and thereby generate the desired field rotation.
Several mass analyzer embodiments are illustrated in the figures of the ""448 patent. In one embodiment, shown in FIGS. 3-9 of the patent, a mass filter chamber is used in which both the first and second electrode pairs are aligned along the same length of the chamber. In a further embodiment, shown in FIG. 10 of the patent, the second electrode pair is displaced from the first electrode pair along the length of the chamber. In each of the foregoing illustrations, the electric field generated at the second electrode pair is out of phase by xcfx80/2 from the electric field generated at the first electrode pair so that the ions are acted upon by at least two distinct electric fields. Thus, at least two orthogonal electric fields are mandated for operation of each of the embodiments specified in the illustrations.
The ions reaching the outlet end of the mass filter chamber form a circle for each set of ions having a given mass-to-charge ratio, m/Q. It is this circular pattern that is analyzed to determine the characteristics of the sample. Accordingly, the ion detector described in the ""448 patent is configured as a two-dimensional device array that must necessarily (and without option) provide and process two coordinate values for each impinging ion. As shown in FIG. 6 of the ""448 patent, the ion detector is disposed immediately adjacent and coextensive with the ion outlet end of the mass filter chamber to ensure detection of substantially all of the ions exiting the mass filter chamber without further regard to their m/Q values.
The present inventors have recognized that existing mass analysis apparatus may be improved in a variety of manners. For example, decreased complexity of one or more components may be achieved by, for example. employing a single, non-rotating RF electric field rather than the rotating field noted above in the ""448 patent. Alternatively, in lieu of, or in addition to the foregoing, improvements can be realized by developing unique ion detection arrangements that take advantage of predetermined ion exit angles from the mass filter for ions having selected m/Q values. Still further, such components can be optimally arranged to concurrently process one or more analytes in parallel with one another to thereby improve the throughput of the analyzer. Such improvements can be achieved while still maintaining or exceeding manufacturing, mass resolution, and/or mass sensitivity goals.
An improved mass analyzer capable of parallel processing one or more analytes is set forth. The mass analyzer comprises a mass filter unit having a plurality of ion selection chambers disposed in parallel with one another. Each of the plurality of ion selection chambers respectively includes an ion inlet lying in an inlet plane and an ion outlet lying in an outlet plane. The mass analyzer further includes a plurality of electrodes disposed in the ion selection chambers and at least one RF signal generator connected to the plurality of electrodes to produce a non-rotating, oscillating electric field in each ion selection chambers. A plurality of ion injectors are each coupled to inject an ion beam into the ion inlet of a respective ion selection chambers. The ions meeting predetermined m/Q requirements pass through the ion selection chambers to contact corresponding detection surfaces of an ion detector array. The mass filter array may also be constructed so that at least one pair of ion selection chambers share at least one common field generating electrode.